Hello gregory_may,

You can declare the return type to be an XmlElement such as

[WebMethod]
public XmlElement MethodX(XmlElement UserInfo, XmlElement DataItem)
{}

The client then has to handle the XML document manually versus having some
wizard parse the individual elements.

Use an XmlTextWriter like yay:
  new XmlTextWriter( new StringWriter );
  .WriteStartDocument()
  .WriteStartElement()
  .WriteAttributeString("whatever")
  // add more stuff
  .WriteEndElement();
  .WriteEndDocument();

Then return the xml string when finished:
  StringWriter.GetStringBuilder().ToString()

Good feedback.  Let me take a look at this.  Probably be a day or two.

Simply create a Structure not a class or XML string.
It will be more easy to work with from the client side with Intelisense.

<WebMethod> _
public function GetUser(byval ID as integer) as User
....
end function

Public Structure User
Public UserName as string
....
End Structure